Re[2]: [fpc-pascal] Last missing benchmark: regex-dna

Пётр Косаревский ppkk at
Fri Oct 6 14:18:03 CEST 2006

> > Basic seems to be: |()?*+ (non-UNICODE) support (from wikipedia).
> | is not basic afaik. From re_format BSD Manpage:
>      Obsolete (``basic'') regular expressions differ in several respects.  `|'
>      is an ordinary character and there is no equivalent for its functional-
>      ity.  `+' and `?' are ordinary characters, and their functionality can
>      be expressed using bounds (`{1,}' or `{0,1}' respectively).  Also note
>      that `x+' in modern REs is equivalent to `xx*'.  The delimiters for
>      bounds are `\{' and `\}', with `{' and `}' by themselves ordinary
>      characters.  The parentheses for nested subexpressions are `\(' and
>      `\)', with `(' and `)' by themselves ordinary characters.  `^' is an
>      ordinary character except at the beginning of the RE or= the beginning
>      of a parenthesized subex- pression, `$' is an ordinary character except
>      at the end of the RE or= the end of a parenthesized subexpression, and
>      `*' is an ordinary charac- ter if it appears at the beginning of the RE
>      or the beginning of a paren- thesized subexpression (after a possible
>      leading `^').  Finally, there is one new type of atom, a back
>      reference: `\' followed by a non-zero deci- mal digit d matches the
>      same sequence of characters matched by the dth parenthesized
>      subexpression (numbering subexpressions by the positions of their
>      opening parentheses, left to right), so that (e.g.) `\([bc]\)\1'
>      matches `bb' or `cc' but not `bc'.

You know the traditional Unix syntax, I quoted wikipedia's definition of "basic regex", and it looks like a simplified POSIX ERE (extended regular expression) syntax ( ).

I've got the idea.

The "last missing benchmark" requires simplest bracket expressions like "[agt]" (equiv. to "(a|g|t)")). Bracketing is supported in FPC "regexpr" enough.

Also it requires substitution (find and replace all) of a regex in a string, which has nothing to do with regex standards.

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